1. Field of the Invention
The present invention relates to a recording head discharging a liquid from discharge orifices by imparting thermal energy to the liquid and to a recording apparatus utilizing the recording head.
2. Description of the Related Art
In an ink jet head, an discharge fault sometimes occurs in all or some of the nozzles as a result of clogging of the nozzles by a foreign substance, or due to air bubbles getting into the ink supply channel or changes in the wettability of the nozzle surface. In particular, in a case that a full-line type ink jet head is used, in which multiple nozzles are disposed so as to span the full width of a recording sheet, important tasks that need to be carried out include identifying nozzles experiencing an discharge fault among the numerous nozzles, so as to compensate a portion of image corresponding to the faulty nozzles, and to reflect the information on the faulty nozzles in ink jet head recovery processing. Furthermore, in printers utilizing this type of ink jet head, the amount of ink discharged from the nozzles may vary depending on temperature variation in the ink jet head, which makes the density of printed images unstable. Suppressing such image degradation due to variation in the amount of discharged ink is especially important in ink jet heads of the above-described full-line type.
In view of the importance of the issue, various ink discharge failure detection techniques, methods of discharge failure compensation, control methods and devices, as well as various methods used for controlling discharged ink amount have been proposed in the past.
According to a configuration disclosed in Japanese Examined Patent Publication No. 04-006549, conductor sections, whose resistance values vary under the action of heat generated by heaters when ink is discharged from nozzles by imparting thermal energy to the ink, are disposed in locations permitting detection of the heat generated by the heaters and the application of discharge signals to the heaters is controlled by detecting variation in the resistance values, i.e. the temperature, of these conductor sections.
Moreover, Japanese Patent No. 2831778 disclosed an ink jet head, in which electro-thermal transducers (heaters) and membrane-type temperature detection elements are provided on the same support, such as a silicon substrate, etc., with the temperature detection elements provided such that they are superimposed on top of the heater array region. The ink jet head herein is composed of a thermal resistance layer used to form the heaters, a layer used to form the temperature sensors, which is arranged as a layer above the heaters and underlies the wiring in non-heater locations, and an insulating layer insulating the thermal resistance layer from the layer that forms the temperature sensors. In another embodiment of Japanese Patent No. 2831778, the heater array area is completely enclosed within the temperature sensor array region, with the temperature sensors arranged such that they are superimposed on top of the heater array as an upper layer. In this manner, it is proposed to improve the accuracy and responsiveness of temperature detection and temperature control.
In the ink jet printer of Japanese Examined Patent Publication No. 04-006549, conductors are disposed in locations, where their resistance values vary under the action of heat generated by the heaters and temperature is detected by detecting the amount of change in the resistance values of the conductors. As described in the document, the application of discharge signals to the heaters is suspended depending on changes in temperature, which correspond to the amount of change in their resistance values. However, the detection circuitry detecting the amount of change in the resistance values of the conductors is not explicitly described. Moreover, no construction or method is disclosed that would be capable of quickly identifying nozzles experiencing a discharge fault.
Furthermore, in the ink jet head of Japanese Patent No. 2831778, the heaters and temperature detection elements are provided on the same support, such as a silicon substrate, etc., and the temperature detection elements, which are formed in the shape of a membrane, are provided such that they are superimposed on top of the heater array region. For this reason, a discharge fault can be quickly detected, but the location of each nozzle experiencing an discharge fault cannot be identified.